Tŷ Du Observatory

The build is under way!! I’ve been taking it slowly but things are progressing nicely. So far I’ve:

• dug a hole 600×600x600mm
• hammered steel rods into the walls of the hole for stability
• filled the hole with concrete
• inserted steel rods in the centre of the concrete where the column will be cast
• started laying foundation blocks
• started assembling the steel shed

I should be able to cast the column either this evening or in the morning after which I’ll continue with the foundations. I’m only using a single block foundation as there’s no weight in the shed and it’ll be supported internally by a wooden frame.

Here’s a before and after shot showing the location of the observatory:

I can’t believe that since dismantling the mount we’ve had the clearest night skies for months. I just have to console myself with the knowledge that it won’t be long until I can take advantage of any gap in the clouds

More to follow…

The observatory build starts next Monday!!  Today I’ve found a major flaw in my plan, but I see it as an opportunity to try something different rather than a show stopper. The plan is to fit the flat plate from the top of the tripod into the depression in a brake disk,  weld the pieces together and bolt the whole lot to the top of a concrete pillar.  I had said I’d build a column form but having looked at my warped timbers I decided to buy a 300mm (outside diameter) x 1 metre tube to cast the column and I found some 10mm brake disks in the bargain bucket at Halfords for £10. I bought M20 threaded bar to sink into the column onto which the disk will fit.  Did you spot the flaw? The piece from the top of the tripod is not steel as I expected but is instead a non-ferous alloy of as yet undermined metals. I have an arc welder, my brother has a mig welder but neither of these will weld alloy to steel!

Putting this minor distraction to one side, the column form will be held in place with a wooden cage (I’ve made that) which will sit on wooden beams laid across the base pit.  The pit will be approx 900mm cubed with the column rising from the centre. I’ll level the cage by driving timbers into the ground at angles then screwing them to the cage to hold it upright. This will have to be done on the day of the concrete pour to make sure everything is as perfect as I can get it. When the concrete is set I’ll build my self-assembly steel shed around the column. I’ll build a wooden frame inside the shed extending to the rear to allow the roof to be slid off.  I’ve found a few examples of this being done online but my favourite, and the one I’m using as inspiration is the Linnhe Observatory in Scotland.

Rather than cast a concrete floor I’ll be laying a waterproof membrane and building a raised wooden floor. The observatory will be for the most part remotely operated so there’s no need to build in creature comforts however I will be including storage for all the astro odds and ends that I’ve collected.

I’ll update this as the project progresses …

A view of the column top. The wooden plate will be removed after the concrete has set leaving a spanner sized gap for tightening the bolt that will hold the EQ6 in place.

This is the tripod top sitting perfectly in the brake-disk. If only I could weld it there. Plan B may involve drilling in from the sides and bolting the two pieces together. Unless I can find someone with a tig welder?

I can’t believe it’s been 4 months since I was last on here! I have done some imaging since the last post but not much, and nothing this year due to the weather conditions. In fact the last time I imaged it snowed and I had to dry my mirror with a hair-dryer. The mirror now has clumps of dust where the snowflakes melted.  I’ll give it a wash before too long.

Anyway, the reason why I thought I’d write something today is to let everyone know that I’m about to build my own roll-off-roof observatory.  I’ve purchased a metal shed which is approx 10′x10′ (3m x 3m) and after searching everywhere for a round section column form to cast the pier I’ve decided to make my own mould from ply which will give a square section, but I have the ply so I can make it at no cost.  I’ve booked 2 weeks off work in March to do the build so I’m currently in the planning stage.

My wife managed to topple the mount this week which luckily didn’t hit anybody or anything on the way down and the only damage appears to be a broken locking lever from the weight shaft.  Its a black cast component that fits over a brass square topped bolt.  I’ll make a new lever when I get a minute. I won’t know if there’s any internal damage until my next viewing/imaging session – fingers crossed.

I’ll take photos and make comments throughout the build so keep watching for updates.

I used an unexpected day at home to make a Hartmann Mask to help me focus the Canon 300D DSLR.  Using the vanes on the secondary to focus has always been good enough with the Atik Camera and even the web cams before, but the the field of view with the Canon means the spikes on the stars are very small and hard to see if they are perfectly formed or not.  After looking at several designs I decided to build the 3 triangle model out of a printer box I had lying around.

Here’s the mask (it’s not really this colour):

The tabs on the side bend over to “hook” over the top of the scope, but in use I had to use some masking tape to hold it in place.

The resulting image when out of focus clearly shows 3 separate images for dimmer stars but shows six large spikes on bright stars like Arcturus here:

When in focus the the 3 images become 1 and the spikes on the bright star become very clear:

The secondary vanes still make spikes so I get an extra 4 to help focusing.

So after focusing the camera (and I think it could do with another tweak), I took a few images before the battery ran out.

M3 Globular Cluster

M13 Globular Cluster

M27 The Dumbbell Nebula

NGC6946 Spiral Galaxy

I’m disappointed that even with 3 minute exposures NGC6946 is still very faint.  With the Atik 16ic this galaxy was brighter using 1 minute exposures – but that’s the difference between a CCD and a CMOS camera I guess.

Next time out I’ll see if I can get the focus even sharper.  I’m also trying to work out how to get the 2″ LPR filter I bought into the light-path given that the camera adapter doesn’t have filter threads.  I’m so glad I haven’t bought a coma corrector yet as this would screw into the same non-existent threads!

I took a couple of 5 minute frames across the “mexico” of the North American Nebula (NGC7000) but they won’t stack so I can only view the frames individually. I’m sure I have caught some nebulosity and comparing my image with others I can make out some structure, but I think I’d need to take lots of these, on a clear night with good seeing and better focus to make anything worth showing here. Maybe next time.

Another clear weekday night, so I can’t image for too long.  I’ve taken a few frames of M51 and M81 and also taken some dark frames before moving the scope back to the Veil.  With time being limited I decided to try 30×120secs initially and I’ll see how they turn out.  I’ve taken a dark frame at the same exposure and iso setting (iso1600) before and I’ll take another after. As I’m imaging remotely it’s not practical to run out between each shot and wait in the cold for 2 minutes while the camera takes a black photo, so I’ll make do with just 2 dark frames.  I haven’t worked out what to do about bias and flats yet.

Here’s a quick and dirty draft image using 14×120 second frames and 1 dark.  I’ve streched and tweaked the image to try and bring out the detail in the nebula, but its still very faint on the left of the image.

The Veil Nebula (NGC6960)

Hopefully I’ll be posting a better image here after I’ve got all the data in.

Another quick effort before wor. I managed to get another 10 shots but DSS only stacked 35 of them.  There’s more detail in there I just need to tease it out using photoshop.

The Veil Nebula (NGC6960) 35x120 seconds

I have another dark frame to add to the stack but I don’t have time at the moment.  Maybe later

Update: Saturday 26th September

I was able to create flats and bias frames as I leave the camera connected to the scope so the light path hasn’t changed since these images were taken the other night.  Reprocessing has annoyingly made things worse not better as there seems to be some structured noise that is accentuated by the new processing.

Example of noise

I’m guessing the noise is a result of imaging at iso1600 rather than adding flats and bias frames but only time will tell as I take more images. Unless someone knows the answer and would like to make a comment

I’m currently trying the same flat frames with the Veil image from the 12th as I’m sure the flats will remove the bright area on the image.  I opened the combined flat in Photo shop and stretched it to find an exact match for my bright area which I may have blamed on coma in a previous post. The iso value of the flats doesn’t match the iso value of the lights so I’m not sure I’m going to get anything, but I’ll keep trying.

—–End Update —–

Session details:

Imaging: Canon 300d (unmodified) – Skywatcher 250 Newtonian scope on EQ6Pro mount

Guiding: PHD -Atik 16ic on 60mm refractor

Processing etc: EQMod, Starry Night, Canon Remote Capture, PHD DSLR Shutter, Deepsky Stacker and PhotoShop CS2